綻び describes a small tear or fray in fabric, and by extension a crack or weakness in something that seems intact. In the song, tears seep out through these tiny “fissures,” making the word a vivid metaphor for hidden emotions gradually breaking through.
King Gnu's "Haretsu" is a song where someone tries to pull a friend out of their own head. It opens with a person at breaking point: "もう精一杯だろ" (You've done all you can, right?), and tears that keep leaking out "小さな綻びから" (from a small tear in the seams). I love that image. The crying is a slow seep from a tiny rip in the fabric, and it is sadder for being so quiet.
The singer's answer is gentle and a bit bossy. He tells her to stop the act: "いつでも強がってないでさ" (Don't always act tough) and "独りぼっちのふりをしてさ" (pretending to be all alone). The line すべては幻 (everything is an illusion) keeps coming back, and it works two ways: the pain might fade like a dream when "朝日は昇り" (the morning sun rises), but it is also an invitation to run. His offer is "めくるめく逃避行の旅へと" (on a dizzying journey of escape), "貴女連れ出すから" (I'll take you away). The word 逃避行 means running away together, close to eloping, and 貴女 is a soft, formal way of saying "you" to a woman. The boldest advice is "目を瞑ればいい" (you can just close your eyes), which is honestly a bit much as life advice, but the song means it as tenderness. And under all that escapism there is one plain instruction: "微かな光を 辿ってさ 生きるんだ" (follow the faint light and live).